Meteorologist Dave Epstein is our go-to person for pressing weather questions on everything from winter blizzards to summer droughts. He’s also a horticulturist, meaning he’s an expert in anything that grows leaves and flowers. GBH's Morning Edition asked our audience for weather and gardening questions, and Epstein graciously answered them on the air. This transcript has been edited for clarity.

Have a gardening or weather question for meteorologist Dave Epstein? Tweet him @GrowingWisdom, email us at, or text 617-300-2008.

What are king tides? Are they becoming more common?

You may have heard the term king tide, often in reference to coastal flooding, or seen waves lapping onto sidewalks along the Boston coastline.

But what is a king tide, exactly?

“It's basically a nonscientific term people use to describe the high tide that occurs during a new or a full moon,” Epstein said.

Higher tides during full or new moons have always existed, Epstein said.

“When you get the full or the new moon, there's more pull on the earth from the moon, so you get bigger tides,” he said. “If you were to look at a chart of tides over the course of every single month, you'd see a high tide that's a little lower than about average, then a little higher than average, and then back to a little lower and then the ultimate low tide again.”

Many other factors can contribute to higher-than-usual tides. Big storms, like nor'easters, can cause storm surges. Topography plays a role too — tides along the Boston Harbor can be about 10 feet, according to National Oceanic and Atmospheric Administration data.

“Big difference, right?” Epstein said. “That's a huge change over the course of those six hours where if you went down to places like Florida, the Gulf Coast, the tides are 1 or 2 feet — much, much less.”

While king tides themselves are not a result of climate change, warmer waters and sea level rise can lead to higher tides than we’d expect without it.

“Over time, because water expands as it gets warmer — the thermal expansion of water — our tides are getting higher,” he said. “We're gaining about .86 feet every century, so just under a foot every 100 years. And that is increasing in terms of rate.”

That might not sound like a lot, he said, but it can make a real difference during high tide. And cities built centuries ago were not always designed with those high tides in mind.

Going forward, he said, urban planners and developers should be consider higher tides when designing along the coast.

“City planners are definitely going to be incorporating this into future buildings,” he said. “Okay, what is it going to be like in [the year] 2123, another foot, at least higher? Now, you added in a nor'easter, now you add in a king tide, now you have problems in Seaport, Back Bay, places like that. And that's what the concern is and the connection between a changing climate and what's always happening, which are bigger tides.”